“A few weeks ago, I watched as some of the world's rarest plants were moved, with the utmost care, into the Temperate House,” he said.

“It was a seminal moment, kicking off the countdown to May's reopening of what has to be Kew Gardens' most incredible building."

Mr Barley added: “Temperate House will be for everyone – from young to old, for budding gardeners or aspiring artists, for those making a pilgrimage from great distances, and for our local community.

“When our first visitors first swing open the doors, they will find these plants encased in a glistening cathedral, the new glass allowing the sun to stream in, the ironwork restored to its glossy best.”